Webhooks System — Notes

Functional

• Register endpoints + subscribed event types.
• Sign payloads (HMAC).
• Retry with backoff.
• DLQ + manual replay.
• Per-endpoint health.

Non-functional

• Delivery within seconds normally; retries can stretch days.
• 99.9% eventual delivery.

Trade-offs

• Fanout architecture matters at scale (one event → many endpoints).
• Customer endpoints flake: design for them.
• Per-endpoint isolation so one slow customer doesn't block others.

Refs

• Stripe webhook architecture blog.
• "Convoys" (avoiding head-of-line blocking) Stripe blog.
• Svix, hookdeck open-source webhook gateways.